Xbase++

Resume an Interrupted FTP Transfer

Demonstrates the RestartNext and PartialTransfer properties, which request that the next transfer resume from existing content and report whether a download was incomplete.

Note: The local paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: For a large transfer over a flaky link, restarting from zero after a drop is wasteful. Setting RestartNext makes the next download continue from the current local file size (and the next upload from the remote size); the flag is consumed by that one transfer and then reset. Afterward PartialTransfer tells you whether the download got only part of the file — the signal to set RestartNext again and resume once more.

Chilkat Xbase++ Downloads

Download Chilkat for Xbase++

Xbase++

LOCAL nSuccess
LOCAL oFtp

nSuccess := 0

oFtp := CreateObject("Chilkat.Ftp2")

oFtp:Hostname := "ftp.example.com"
oFtp:Username := "myFtpLogin"

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
oFtp:Password := "myPassword"

nSuccess := oFtp:Connect()
IF (nSuccess == 0)
    ? oFtp:LastErrorText
    oFtp:destroy()
    RETURN
ENDIF

//  RestartNext requests that the NEXT transfer resume from existing content rather than starting
//  over.  It is consumed by that transfer and then automatically reset.
oFtp:RestartNext := 1

//  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
//  the current local file size.
nSuccess := oFtp:GetFile("public_html/bigfile.zip", "qa_output/bigfile.zip")
IF (nSuccess == 0)
    ? oFtp:LastErrorText
    oFtp:destroy()
    RETURN
ENDIF

//  PartialTransfer indicates whether the most recent download received some, but not all, of the
//  remote file -- distinguishing a mid-transfer failure from other outcomes.
IF (oFtp:PartialTransfer)
    ? "Only part of the file was received; another resume may be needed."
ELSE
    ? "The file was fully received."
ENDIF

nSuccess := oFtp:Disconnect()
IF (nSuccess == 0)
    ? oFtp:LastErrorText
    oFtp:destroy()
    RETURN
ENDIF

oFtp:destroy()